code: def _align_add_bias(bias, index, keys, series):
      "Realign a bias series with an index, and add to a series"
      # realign bias to make sure it matches
      bias = bias.reindex(index, fill_value=0)
      assert len(bias) == len(index)
      # look up bias for each key
      ibs = bias.loc[keys]
      # change index
      ibs.index = keys.index
      # and add
      series = series + ibs
      return bias, series
  
imports: import logging
  import time
  import pandas
  import numpy
  import numba
  from seedbank import numpy_rng
  from .bias import Bias
  from .mf_common import MFPredictor
  from ..None import util
label_desc: Use image node_id 6 for calling a global function with example usage: _align_add_bias(bias, index, keys, series) and returns: bias,  series